[Gate-users] low energy and standard mode

[Chen, Yu]

-----Original Message-----
From: gate-users-bounces at lists.healthgrid.org on behalf of Sanae Rechka
Sent: Wed 1/2/2008 11:19 PM
To: gate-users at lists.healthgrid.org
Subject: [Gate-users] low energy and standard mode
 

> Dear Gate users,

> I would like to ask you please if it's better to use low energy mode or standard
> mode for 511 keV. I would like also to mention that according to the Hits

The standard EM model is a parameterized model and is optimized to high energy application,
which guarantees a 5% uncertainty above 10 keV according to Geant4. There is no Rayleigh
scattering process implemented in the standard model since its cross section in high energy region
is very low.

On the other hand, the low energy model is a data-driven model which utilizes the measured cross section
data for photoelectric, Compton, Rayleigh processes (G4EMLow data lib). This model gives more precise 
results in low energy region. 

For 511 keV, there is not much difference with two models especially for photoelectric process, but the standard model
is more computing-efficient.

> output file generated, when using the standard mode the energy deposited by
> Compton interaction is 0 which is normal. But when using the low energy mode
> there is some energy associated to Compton interaction, in this second case
> what does this energy represent ?


Do you have such an energy distribution plot?
What is your Geant4 and G4EMLow versions? 

If possible, can you compile different G4EMLOW v3 or v4 into the same Geant4, GATE version to see any difference?

Yu

> Thank you

> Happy new year too

> Sanae
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Yu Chen, Ph.D.
University of Massachusetts Medical School
Division of Nuclear Medicine
55 Lake Avenue North
Worcester, MA 01655-0243
Phone:  (508) 856-6123
Fax:    (508) 856-4572


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